// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

package org.rocksdb;

import java.util.Collection;
import java.util.List;

public interface DBOptionsInterface<T extends DBOptionsInterface> {

  /**
   * Use this if your DB is very small (like under 1GB) and you don't want to
   * spend lots of memory for memtables.
   *
   * @return the instance of the current object.
   */
  T optimizeForSmallDb();

  /**
   * Use the specified object to interact with the environment,
   * e.g. to read/write files, schedule background work, etc.
   * Default: {@link Env#getDefault()}
   *
   * @param env {@link Env} instance.
   * @return the instance of the current Options.
   */
  T setEnv(final Env env);

  /**
   * Returns the set RocksEnv instance.
   *
   * @return {@link RocksEnv} instance set in the options.
   */
  Env getEnv();

  /**
   * <p>By default, RocksDB uses only one background thread for flush and
   * compaction. Calling this function will set it up such that total of
   * `total_threads` is used.</p>
   *
   * <p>You almost definitely want to call this function if your system is
   * bottlenecked by RocksDB.</p>
   *
   * @param totalThreads The total number of threads to be used by RocksDB.
   *     A good value is the number of cores.
   *
   * @return the instance of the current Options
   */
  T setIncreaseParallelism(int totalThreads);

  /**
   * If this value is set to true, then the database will be created
   * if it is missing during {@code RocksDB.open()}.
   * Default: false
   *
   * @param flag a flag indicating whether to create a database the
   *     specified database in {@link RocksDB#open(org.rocksdb.Options, String)} operation
   *     is missing.
   * @return the instance of the current Options
   * @see RocksDB#open(org.rocksdb.Options, String)
   */
  T setCreateIfMissing(boolean flag);

  /**
   * Return true if the create_if_missing flag is set to true.
   * If true, the database will be created if it is missing.
   *
   * @return true if the createIfMissing option is set to true.
   * @see #setCreateIfMissing(boolean)
   */
  boolean createIfMissing();

  /**
   * <p>If true, missing column families will be automatically created</p>
   *
   * <p>Default: false</p>
   *
   * @param flag a flag indicating if missing column families shall be
   *     created automatically.
   * @return true if missing column families shall be created automatically
   *     on open.
   */
  T setCreateMissingColumnFamilies(boolean flag);

  /**
   * Return true if the create_missing_column_families flag is set
   * to true. If true column families be created if missing.
   *
   * @return true if the createMissingColumnFamilies is set to
   *     true.
   * @see #setCreateMissingColumnFamilies(boolean)
   */
  boolean createMissingColumnFamilies();

  /**
   * If true, an error will be thrown during RocksDB.open() if the
   * database already exists.
   * Default: false
   *
   * @param errorIfExists if true, an exception will be thrown
   *     during {@code RocksDB.open()} if the database already exists.
   * @return the reference to the current option.
   * @see RocksDB#open(org.rocksdb.Options, String)
   */
  T setErrorIfExists(boolean errorIfExists);

  /**
   * If true, an error will be thrown during RocksDB.open() if the
   * database already exists.
   *
   * @return if true, an error is raised when the specified database
   *    already exists before open.
   */
  boolean errorIfExists();

  /**
   * If true, the implementation will do aggressive checking of the
   * data it is processing and will stop early if it detects any
   * errors.  This may have unforeseen ramifications: for example, a
   * corruption of one DB entry may cause a large number of entries to
   * become unreadable or for the entire DB to become unopenable.
   * If any of the  writes to the database fails (Put, Delete, Merge, Write),
   * the database will switch to read-only mode and fail all other
   * Write operations.
   * Default: true
   *
   * @param paranoidChecks a flag to indicate whether paranoid-check
   *     is on.
   * @return the reference to the current option.
   */
  T setParanoidChecks(boolean paranoidChecks);

  /**
   * If true, the implementation will do aggressive checking of the
   * data it is processing and will stop early if it detects any
   * errors.  This may have unforeseen ramifications: for example, a
   * corruption of one DB entry may cause a large number of entries to
   * become unreadable or for the entire DB to become unopenable.
   * If any of the  writes to the database fails (Put, Delete, Merge, Write),
   * the database will switch to read-only mode and fail all other
   * Write operations.
   *
   * @return a boolean indicating whether paranoid-check is on.
   */
  boolean paranoidChecks();

  /**
   * Use to control write rate of flush and compaction. Flush has higher
   * priority than compaction. Rate limiting is disabled if nullptr.
   * Default: nullptr
   *
   * @param rateLimiter {@link org.rocksdb.RateLimiter} instance.
   * @return the instance of the current object.
   *
   * @since 3.10.0
   */
  T setRateLimiter(RateLimiter rateLimiter);

  /**
   * <p>Any internal progress/error information generated by
   * the db will be written to the Logger if it is non-nullptr,
   * or to a file stored in the same directory as the DB
   * contents if info_log is nullptr.</p>
   *
   * <p>Default: nullptr</p>
   *
   * @param logger {@link Logger} instance.
   * @return the instance of the current object.
   */
  T setLogger(Logger logger);

  /**
   * <p>Sets the RocksDB log level. Default level is INFO</p>
   *
   * @param infoLogLevel log level to set.
   * @return the instance of the current object.
   */
  T setInfoLogLevel(InfoLogLevel infoLogLevel);

  /**
   * <p>Returns currently set log level.</p>
   * @return {@link org.rocksdb.InfoLogLevel} instance.
   */
  InfoLogLevel infoLogLevel();

  /**
   * Number of open files that can be used by the DB.  You may need to
   * increase this if your database has a large working set. Value -1 means
   * files opened are always kept open. You can estimate number of files based
   * on {@code target_file_size_base} and {@code target_file_size_multiplier}
   * for level-based compaction. For universal-style compaction, you can usually
   * set it to -1.
   * Default: 5000
   *
   * @param maxOpenFiles the maximum number of open files.
   * @return the instance of the current object.
   */
  T setMaxOpenFiles(int maxOpenFiles);

  /**
   * Number of open files that can be used by the DB.  You may need to
   * increase this if your database has a large working set. Value -1 means
   * files opened are always kept open. You can estimate number of files based
   * on {@code target_file_size_base} and {@code target_file_size_multiplier}
   * for level-based compaction. For universal-style compaction, you can usually
   * set it to -1.
   *
   * @return the maximum number of open files.
   */
  int maxOpenFiles();

  /**
   * If {@link #maxOpenFiles()} is -1, DB will open all files on DB::Open(). You
   * can use this option to increase the number of threads used to open the
   * files.
   *
   * Default: 16
   *
   * @param maxFileOpeningThreads the maximum number of threads to use to
   *     open files
   *
   * @return the reference to the current options.
   */
  T setMaxFileOpeningThreads(int maxFileOpeningThreads);

  /**
   * If {@link #maxOpenFiles()} is -1, DB will open all files on DB::Open(). You
   * can use this option to increase the number of threads used to open the
   * files.
   *
   * Default: 16
   *
   * @return the maximum number of threads to use to open files
   */
  int maxFileOpeningThreads();

  /**
   * <p>Once write-ahead logs exceed this size, we will start forcing the
   * flush of column families whose memtables are backed by the oldest live
   * WAL file (i.e. the ones that are causing all the space amplification).
   * </p>
   * <p>If set to 0 (default), we will dynamically choose the WAL size limit to
   * be [sum of all write_buffer_size * max_write_buffer_number] * 2</p>
   * <p>Default: 0</p>
   *
   * @param maxTotalWalSize max total wal size.
   * @return the instance of the current object.
   */
  T setMaxTotalWalSize(long maxTotalWalSize);

  /**
   * <p>Returns the max total wal size. Once write-ahead logs exceed this size,
   * we will start forcing the flush of column families whose memtables are
   * backed by the oldest live WAL file (i.e. the ones that are causing all
   * the space amplification).</p>
   *
   * <p>If set to 0 (default), we will dynamically choose the WAL size limit
   * to be [sum of all write_buffer_size * max_write_buffer_number] * 2
   * </p>
   *
   * @return max total wal size
   */
  long maxTotalWalSize();

  /**
   * <p>Sets the statistics object which collects metrics about database operations.
   * Statistics objects should not be shared between DB instances as
   * it does not use any locks to prevent concurrent updates.</p>
   *
   * @param statistics The statistics to set
   *
   * @return the instance of the current object.
   *
   * @see RocksDB#open(org.rocksdb.Options, String)
   */
  T setStatistics(final Statistics statistics);

  /**
   * <p>Returns statistics object.</p>
   *
   * @return the instance of the statistics object or null if there is no
   * statistics object.
   *
   * @see #setStatistics(Statistics)
   */
  Statistics statistics();

  /**
   * <p>If true, then every store to stable storage will issue a fsync.</p>
   * <p>If false, then every store to stable storage will issue a fdatasync.
   * This parameter should be set to true while storing data to
   * filesystem like ext3 that can lose files after a reboot.</p>
   * <p>Default: false</p>
   *
   * @param useFsync a boolean flag to specify whether to use fsync
   * @return the instance of the current object.
   */
  T setUseFsync(boolean useFsync);

  /**
   * <p>If true, then every store to stable storage will issue a fsync.</p>
   * <p>If false, then every store to stable storage will issue a fdatasync.
   * This parameter should be set to true while storing data to
   * filesystem like ext3 that can lose files after a reboot.</p>
   *
   * @return boolean value indicating if fsync is used.
   */
  boolean useFsync();

  /**
   * A list of paths where SST files can be put into, with its target size.
   * Newer data is placed into paths specified earlier in the vector while
   * older data gradually moves to paths specified later in the vector.
   *
   * For example, you have a flash device with 10GB allocated for the DB,
   * as well as a hard drive of 2TB, you should config it to be:
   *    [{"/flash_path", 10GB}, {"/hard_drive", 2TB}]
   *
   * The system will try to guarantee data under each path is close to but
   * not larger than the target size. But current and future file sizes used
   * by determining where to place a file are based on best-effort estimation,
   * which means there is a chance that the actual size under the directory
   * is slightly more than target size under some workloads. User should give
   * some buffer room for those cases.
   *
   * If none of the paths has sufficient room to place a file, the file will
   * be placed to the last path anyway, despite to the target size.
   *
   * Placing newer data to earlier paths is also best-efforts. User should
   * expect user files to be placed in higher levels in some extreme cases.
   *
   * If left empty, only one path will be used, which is db_name passed when
   * opening the DB.
   *
   * Default: empty
   *
   * @param dbPaths the paths and target sizes
   *
   * @return the reference to the current options
   */
  T setDbPaths(final Collection<DbPath> dbPaths);

  /**
   * A list of paths where SST files can be put into, with its target size.
   * Newer data is placed into paths specified earlier in the vector while
   * older data gradually moves to paths specified later in the vector.
   *
   * For example, you have a flash device with 10GB allocated for the DB,
   * as well as a hard drive of 2TB, you should config it to be:
   *    [{"/flash_path", 10GB}, {"/hard_drive", 2TB}]
   *
   * The system will try to guarantee data under each path is close to but
   * not larger than the target size. But current and future file sizes used
   * by determining where to place a file are based on best-effort estimation,
   * which means there is a chance that the actual size under the directory
   * is slightly more than target size under some workloads. User should give
   * some buffer room for those cases.
   *
   * If none of the paths has sufficient room to place a file, the file will
   * be placed to the last path anyway, despite to the target size.
   *
   * Placing newer data to earlier paths is also best-efforts. User should
   * expect user files to be placed in higher levels in some extreme cases.
   *
   * If left empty, only one path will be used, which is db_name passed when
   * opening the DB.
   *
   * Default: {@link java.util.Collections#emptyList()}
   *
   * @return dbPaths the paths and target sizes
   */
  List<DbPath> dbPaths();

  /**
   * This specifies the info LOG dir.
   * If it is empty, the log files will be in the same dir as data.
   * If it is non empty, the log files will be in the specified dir,
   * and the db data dir's absolute path will be used as the log file
   * name's prefix.
   *
   * @param dbLogDir the path to the info log directory
   * @return the instance of the current object.
   */
  T setDbLogDir(String dbLogDir);

  /**
   * Returns the directory of info log.
   *
   * If it is empty, the log files will be in the same dir as data.
   * If it is non empty, the log files will be in the specified dir,
   * and the db data dir's absolute path will be used as the log file
   * name's prefix.
   *
   * @return the path to the info log directory
   */
  String dbLogDir();

  /**
   * This specifies the absolute dir path for write-ahead logs (WAL).
   * If it is empty, the log files will be in the same dir as data,
   *   dbname is used as the data dir by default
   * If it is non empty, the log files will be in kept the specified dir.
   * When destroying the db,
   *   all log files in wal_dir and the dir itself is deleted
   *
   * @param walDir the path to the write-ahead-log directory.
   * @return the instance of the current object.
   */
  T setWalDir(String walDir);

  /**
   * Returns the path to the write-ahead-logs (WAL) directory.
   *
   * If it is empty, the log files will be in the same dir as data,
   *   dbname is used as the data dir by default
   * If it is non empty, the log files will be in kept the specified dir.
   * When destroying the db,
   *   all log files in wal_dir and the dir itself is deleted
   *
   * @return the path to the write-ahead-logs (WAL) directory.
   */
  String walDir();

  /**
   * The periodicity when obsolete files get deleted. The default
   * value is 6 hours. The files that get out of scope by compaction
   * process will still get automatically delete on every compaction,
   * regardless of this setting
   *
   * @param micros the time interval in micros
   * @return the instance of the current object.
   */
  T setDeleteObsoleteFilesPeriodMicros(long micros);

  /**
   * The periodicity when obsolete files get deleted. The default
   * value is 6 hours. The files that get out of scope by compaction
   * process will still get automatically delete on every compaction,
   * regardless of this setting
   *
   * @return the time interval in micros when obsolete files will be deleted.
   */
  long deleteObsoleteFilesPeriodMicros();

  /**
   * Suggested number of concurrent background compaction jobs, submitted to
   * the default LOW priority thread pool.
   * Default: 1
   *
   * @param baseBackgroundCompactions Suggested number of background compaction
   *     jobs
   *
   * @deprecated Use {@link #setMaxBackgroundJobs(int)}
   */
  void setBaseBackgroundCompactions(int baseBackgroundCompactions);

  /**
   * Suggested number of concurrent background compaction jobs, submitted to
   * the default LOW priority thread pool.
   * Default: 1
   *
   * @return Suggested number of background compaction jobs
   */
  int baseBackgroundCompactions();

  /**
   * Specifies the maximum number of concurrent background compaction jobs,
   * submitted to the default LOW priority thread pool.
   * If you're increasing this, also consider increasing number of threads in
   * LOW priority thread pool. For more information, see
   * Default: 1
   *
   * @param maxBackgroundCompactions the maximum number of background
   *     compaction jobs.
   * @return the instance of the current object.
   *
   * @see RocksEnv#setBackgroundThreads(int)
   * @see RocksEnv#setBackgroundThreads(int, int)
   * @see #maxBackgroundFlushes()
   */
  T setMaxBackgroundCompactions(int maxBackgroundCompactions);

  /**
   * Returns the maximum number of concurrent background compaction jobs,
   * submitted to the default LOW priority thread pool.
   * When increasing this number, we may also want to consider increasing
   * number of threads in LOW priority thread pool.
   * Default: 1
   *
   * @return the maximum number of concurrent background compaction jobs.
   * @see RocksEnv#setBackgroundThreads(int)
   * @see RocksEnv#setBackgroundThreads(int, int)
   *
   * @deprecated Use {@link #setMaxBackgroundJobs(int)}
   */
  int maxBackgroundCompactions();

  /**
   * This value represents the maximum number of threads that will
   * concurrently perform a compaction job by breaking it into multiple,
   * smaller ones that are run simultaneously.
   * Default: 1 (i.e. no subcompactions)
   *
   * @param maxSubcompactions The maximum number of threads that will
   *     concurrently perform a compaction job
   */
  void setMaxSubcompactions(int maxSubcompactions);

  /**
   * This value represents the maximum number of threads that will
   * concurrently perform a compaction job by breaking it into multiple,
   * smaller ones that are run simultaneously.
   * Default: 1 (i.e. no subcompactions)
   *
   * @return The maximum number of threads that will concurrently perform a
   *     compaction job
   */
  int maxSubcompactions();

  /**
   * Specifies the maximum number of concurrent background flush jobs.
   * If you're increasing this, also consider increasing number of threads in
   * HIGH priority thread pool. For more information, see
   * Default: 1
   *
   * @param maxBackgroundFlushes number of max concurrent flush jobs
   * @return the instance of the current object.
   *
   * @see RocksEnv#setBackgroundThreads(int)
   * @see RocksEnv#setBackgroundThreads(int, int)
   * @see #maxBackgroundCompactions()
   *
   * @deprecated Use {@link #setMaxBackgroundJobs(int)}
   */
  T setMaxBackgroundFlushes(int maxBackgroundFlushes);

  /**
   * Returns the maximum number of concurrent background flush jobs.
   * If you're increasing this, also consider increasing number of threads in
   * HIGH priority thread pool. For more information, see
   * Default: 1
   *
   * @return the maximum number of concurrent background flush jobs.
   * @see RocksEnv#setBackgroundThreads(int)
   * @see RocksEnv#setBackgroundThreads(int, int)
   */
  int maxBackgroundFlushes();

  /**
   * Specifies the maximum number of concurrent background jobs (both flushes
   * and compactions combined).
   * Default: 2
   *
   * @param maxBackgroundJobs number of max concurrent background jobs
   * @return the instance of the current object.
   */
  T setMaxBackgroundJobs(int maxBackgroundJobs);

  /**
   * Returns the maximum number of concurrent background jobs (both flushes
   * and compactions combined).
   * Default: 2
   *
   * @return the maximum number of concurrent background jobs.
   */
  int maxBackgroundJobs();

  /**
   * Specifies the maximum size of a info log file. If the current log file
   * is larger than `max_log_file_size`, a new info log file will
   * be created.
   * If 0, all logs will be written to one log file.
   *
   * @param maxLogFileSize the maximum size of a info log file.
   * @return the instance of the current object.
   * @throws java.lang.IllegalArgumentException thrown on 32-Bit platforms
   *   while overflowing the underlying platform specific value.
   */
  T setMaxLogFileSize(long maxLogFileSize);

  /**
   * Returns the maximum size of a info log file. If the current log file
   * is larger than this size, a new info log file will be created.
   * If 0, all logs will be written to one log file.
   *
   * @return the maximum size of the info log file.
   */
  long maxLogFileSize();

  /**
   * Specifies the time interval for the info log file to roll (in seconds).
   * If specified with non-zero value, log file will be rolled
   * if it has been active longer than `log_file_time_to_roll`.
   * Default: 0 (disabled)
   *
   * @param logFileTimeToRoll the time interval in seconds.
   * @return the instance of the current object.
   * @throws java.lang.IllegalArgumentException thrown on 32-Bit platforms
   *   while overflowing the underlying platform specific value.
   */
  T setLogFileTimeToRoll(long logFileTimeToRoll);

  /**
   * Returns the time interval for the info log file to roll (in seconds).
   * If specified with non-zero value, log file will be rolled
   * if it has been active longer than `log_file_time_to_roll`.
   * Default: 0 (disabled)
   *
   * @return the time interval in seconds.
   */
  long logFileTimeToRoll();

  /**
   * Specifies the maximum number of info log files to be kept.
   * Default: 1000
   *
   * @param keepLogFileNum the maximum number of info log files to be kept.
   * @return the instance of the current object.
   * @throws java.lang.IllegalArgumentException thrown on 32-Bit platforms
   *   while overflowing the underlying platform specific value.
   */
  T setKeepLogFileNum(long keepLogFileNum);

  /**
   * Returns the maximum number of info log files to be kept.
   * Default: 1000
   *
   * @return the maximum number of info log files to be kept.
   */
  long keepLogFileNum();

  /**
   * Recycle log files.
   *
   * If non-zero, we will reuse previously written log files for new
   * logs, overwriting the old data.  The value indicates how many
   * such files we will keep around at any point in time for later
   * use.
   *
   * This is more efficient because the blocks are already
   * allocated and fdatasync does not need to update the inode after
   * each write.
   *
   * Default: 0
   *
   * @param recycleLogFileNum the number of log files to keep for recycling
   *
   * @return the reference to the current options
   */
  T setRecycleLogFileNum(long recycleLogFileNum);

  /**
   * Recycle log files.
   *
   * If non-zero, we will reuse previously written log files for new
   * logs, overwriting the old data.  The value indicates how many
   * such files we will keep around at any point in time for later
   * use.
   *
   * This is more efficient because the blocks are already
   * allocated and fdatasync does not need to update the inode after
   * each write.
   *
   * Default: 0
   *
   * @return the number of log files kept for recycling
   */
  long recycleLogFileNum();

  /**
   * Manifest file is rolled over on reaching this limit.
   * The older manifest file be deleted.
   * The default value is MAX_INT so that roll-over does not take place.
   *
   * @param maxManifestFileSize the size limit of a manifest file.
   * @return the instance of the current object.
   */
  T setMaxManifestFileSize(long maxManifestFileSize);

  /**
   * Manifest file is rolled over on reaching this limit.
   * The older manifest file be deleted.
   * The default value is MAX_INT so that roll-over does not take place.
   *
   * @return the size limit of a manifest file.
   */
  long maxManifestFileSize();

  /**
   * Number of shards used for table cache.
   *
   * @param tableCacheNumshardbits the number of chards
   * @return the instance of the current object.
   */
  T setTableCacheNumshardbits(int tableCacheNumshardbits);

  /**
   * Number of shards used for table cache.
   *
   * @return the number of shards used for table cache.
   */
  int tableCacheNumshardbits();

  /**
   * {@link #walTtlSeconds()} and {@link #walSizeLimitMB()} affect how archived logs
   * will be deleted.
   * <ol>
   * <li>If both set to 0, logs will be deleted asap and will not get into
   * the archive.</li>
   * <li>If WAL_ttl_seconds is 0 and WAL_size_limit_MB is not 0,
   *    WAL files will be checked every 10 min and if total size is greater
   *    then WAL_size_limit_MB, they will be deleted starting with the
   *    earliest until size_limit is met. All empty files will be deleted.</li>
   * <li>If WAL_ttl_seconds is not 0 and WAL_size_limit_MB is 0, then
   *    WAL files will be checked every WAL_ttl_secondsi / 2 and those that
   *    are older than WAL_ttl_seconds will be deleted.</li>
   * <li>If both are not 0, WAL files will be checked every 10 min and both
   *    checks will be performed with ttl being first.</li>
   * </ol>
   *
   * @param walTtlSeconds the ttl seconds
   * @return the instance of the current object.
   * @see #setWalSizeLimitMB(long)
   */
  T setWalTtlSeconds(long walTtlSeconds);

  /**
   * WalTtlSeconds() and walSizeLimitMB() affect how archived logs
   * will be deleted.
   * <ol>
   * <li>If both set to 0, logs will be deleted asap and will not get into
   * the archive.</li>
   * <li>If WAL_ttl_seconds is 0 and WAL_size_limit_MB is not 0,
   * WAL files will be checked every 10 min and if total size is greater
   * then WAL_size_limit_MB, they will be deleted starting with the
   * earliest until size_limit is met. All empty files will be deleted.</li>
   * <li>If WAL_ttl_seconds is not 0 and WAL_size_limit_MB is 0, then
   * WAL files will be checked every WAL_ttl_secondsi / 2 and those that
   * are older than WAL_ttl_seconds will be deleted.</li>
   * <li>If both are not 0, WAL files will be checked every 10 min and both
   * checks will be performed with ttl being first.</li>
   * </ol>
   *
   * @return the wal-ttl seconds
   * @see #walSizeLimitMB()
   */
  long walTtlSeconds();

  /**
   * WalTtlSeconds() and walSizeLimitMB() affect how archived logs
   * will be deleted.
   * <ol>
   * <li>If both set to 0, logs will be deleted asap and will not get into
   *    the archive.</li>
   * <li>If WAL_ttl_seconds is 0 and WAL_size_limit_MB is not 0,
   *    WAL files will be checked every 10 min and if total size is greater
   *    then WAL_size_limit_MB, they will be deleted starting with the
   *    earliest until size_limit is met. All empty files will be deleted.</li>
   * <li>If WAL_ttl_seconds is not 0 and WAL_size_limit_MB is 0, then
   *    WAL files will be checked every WAL_ttl_secondsi / 2 and those that
   *    are older than WAL_ttl_seconds will be deleted.</li>
   * <li>If both are not 0, WAL files will be checked every 10 min and both
   *    checks will be performed with ttl being first.</li>
   * </ol>
   *
   * @param sizeLimitMB size limit in mega-bytes.
   * @return the instance of the current object.
   * @see #setWalSizeLimitMB(long)
   */
  T setWalSizeLimitMB(long sizeLimitMB);

  /**
   * {@link #walTtlSeconds()} and {@code #walSizeLimitMB()} affect how archived logs
   * will be deleted.
   * <ol>
   * <li>If both set to 0, logs will be deleted asap and will not get into
   *    the archive.</li>
   * <li>If WAL_ttl_seconds is 0 and WAL_size_limit_MB is not 0,
   *    WAL files will be checked every 10 min and if total size is greater
   *    then WAL_size_limit_MB, they will be deleted starting with the
   *    earliest until size_limit is met. All empty files will be deleted.</li>
   * <li>If WAL_ttl_seconds is not 0 and WAL_size_limit_MB is 0, then
   *    WAL files will be checked every WAL_ttl_seconds i / 2 and those that
   *    are older than WAL_ttl_seconds will be deleted.</li>
   * <li>If both are not 0, WAL files will be checked every 10 min and both
   *    checks will be performed with ttl being first.</li>
   * </ol>
   * @return size limit in mega-bytes.
   * @see #walSizeLimitMB()
   */
  long walSizeLimitMB();

  /**
   * Number of bytes to preallocate (via fallocate) the manifest
   * files.  Default is 4mb, which is reasonable to reduce random IO
   * as well as prevent overallocation for mounts that preallocate
   * large amounts of data (such as xfs's allocsize option).
   *
   * @param size the size in byte
   * @return the instance of the current object.
   * @throws java.lang.IllegalArgumentException thrown on 32-Bit platforms
   *   while overflowing the underlying platform specific value.
   */
  T setManifestPreallocationSize(long size);

  /**
   * Number of bytes to preallocate (via fallocate) the manifest
   * files.  Default is 4mb, which is reasonable to reduce random IO
   * as well as prevent overallocation for mounts that preallocate
   * large amounts of data (such as xfs's allocsize option).
   *
   * @return size in bytes.
   */
  long manifestPreallocationSize();

  /**
   * Enable the OS to use direct I/O for reading sst tables.
   * Default: false
   *
   * @param useDirectReads if true, then direct read is enabled
   * @return the instance of the current object.
   */
  T setUseDirectReads(boolean useDirectReads);

  /**
   * Enable the OS to use direct I/O for reading sst tables.
   * Default: false
   *
   * @return if true, then direct reads are enabled
   */
  boolean useDirectReads();

  /**
   * Enable the OS to use direct reads and writes in flush and
   * compaction
   * Default: false
   *
   * @param useDirectIoForFlushAndCompaction if true, then direct
   *        I/O will be enabled for background flush and compactions
   * @return the instance of the current object.
   */
  T setUseDirectIoForFlushAndCompaction(boolean useDirectIoForFlushAndCompaction);

  /**
   * Enable the OS to use direct reads and writes in flush and
   * compaction
   *
   * @return if true, then direct I/O is enabled for flush and
   *         compaction
   */
  boolean useDirectIoForFlushAndCompaction();

  /**
   * Whether fallocate calls are allowed
   *
   * @param allowFAllocate false if fallocate() calls are bypassed
   *
   * @return the reference to the current options.
   */
  T setAllowFAllocate(boolean allowFAllocate);

  /**
   * Whether fallocate calls are allowed
   *
   * @return false if fallocate() calls are bypassed
   */
  boolean allowFAllocate();

  /**
   * Allow the OS to mmap file for reading sst tables.
   * Default: false
   *
   * @param allowMmapReads true if mmap reads are allowed.
   * @return the instance of the current object.
   */
  T setAllowMmapReads(boolean allowMmapReads);

  /**
   * Allow the OS to mmap file for reading sst tables.
   * Default: false
   *
   * @return true if mmap reads are allowed.
   */
  boolean allowMmapReads();

  /**
   * Allow the OS to mmap file for writing. Default: false
   *
   * @param allowMmapWrites true if mmap writes are allowd.
   * @return the instance of the current object.
   */
  T setAllowMmapWrites(boolean allowMmapWrites);

  /**
   * Allow the OS to mmap file for writing. Default: false
   *
   * @return true if mmap writes are allowed.
   */
  boolean allowMmapWrites();

  /**
   * Disable child process inherit open files. Default: true
   *
   * @param isFdCloseOnExec true if child process inheriting open
   *     files is disabled.
   * @return the instance of the current object.
   */
  T setIsFdCloseOnExec(boolean isFdCloseOnExec);

  /**
   * Disable child process inherit open files. Default: true
   *
   * @return true if child process inheriting open files is disabled.
   */
  boolean isFdCloseOnExec();

  /**
   * if not zero, dump rocksdb.stats to LOG every stats_dump_period_sec
   * Default: 600 (10 minutes)
   *
   * @param statsDumpPeriodSec time interval in seconds.
   * @return the instance of the current object.
   */
  T setStatsDumpPeriodSec(int statsDumpPeriodSec);

  /**
   * If not zero, dump rocksdb.stats to LOG every stats_dump_period_sec
   * Default: 600 (10 minutes)
   *
   * @return time interval in seconds.
   */
  int statsDumpPeriodSec();

  /**
   * If set true, will hint the underlying file system that the file
   * access pattern is random, when a sst file is opened.
   * Default: true
   *
   * @param adviseRandomOnOpen true if hinting random access is on.
   * @return the instance of the current object.
   */
  T setAdviseRandomOnOpen(boolean adviseRandomOnOpen);

  /**
   * If set true, will hint the underlying file system that the file
   * access pattern is random, when a sst file is opened.
   * Default: true
   *
   * @return true if hinting random access is on.
   */
  boolean adviseRandomOnOpen();

  /**
   * Amount of data to build up in memtables across all column
   * families before writing to disk.
   *
   * This is distinct from {@link ColumnFamilyOptions#writeBufferSize()},
   * which enforces a limit for a single memtable.
   *
   * This feature is disabled by default. Specify a non-zero value
   * to enable it.
   *
   * Default: 0 (disabled)
   *
   * @param dbWriteBufferSize the size of the write buffer
   *
   * @return the reference to the current options.
   */
  T setDbWriteBufferSize(long dbWriteBufferSize);

  /**
   * Amount of data to build up in memtables across all column
   * families before writing to disk.
   *
   * This is distinct from {@link ColumnFamilyOptions#writeBufferSize()},
   * which enforces a limit for a single memtable.
   *
   * This feature is disabled by default. Specify a non-zero value
   * to enable it.
   *
   * Default: 0 (disabled)
   *
   * @return the size of the write buffer
   */
  long dbWriteBufferSize();

  /**
   * Specify the file access pattern once a compaction is started.
   * It will be applied to all input files of a compaction.
   *
   * Default: {@link AccessHint#NORMAL}
   *
   * @param accessHint The access hint
   *
   * @return the reference to the current options.
   */
  T setAccessHintOnCompactionStart(final AccessHint accessHint);

  /**
   * Specify the file access pattern once a compaction is started.
   * It will be applied to all input files of a compaction.
   *
   * Default: {@link AccessHint#NORMAL}
   *
   * @return The access hint
   */
  AccessHint accessHintOnCompactionStart();

  /**
   * If true, always create a new file descriptor and new table reader
   * for compaction inputs. Turn this parameter on may introduce extra
   * memory usage in the table reader, if it allocates extra memory
   * for indexes. This will allow file descriptor prefetch options
   * to be set for compaction input files and not to impact file
   * descriptors for the same file used by user queries.
   * Suggest to enable {@link BlockBasedTableConfig#cacheIndexAndFilterBlocks()}
   * for this mode if using block-based table.
   *
   * Default: false
   *
   * @param newTableReaderForCompactionInputs true if a new file descriptor and
   *     table reader should be created for compaction inputs
   *
   * @return the reference to the current options.
   */
  T setNewTableReaderForCompactionInputs(
      boolean newTableReaderForCompactionInputs);

  /**
   * If true, always create a new file descriptor and new table reader
   * for compaction inputs. Turn this parameter on may introduce extra
   * memory usage in the table reader, if it allocates extra memory
   * for indexes. This will allow file descriptor prefetch options
   * to be set for compaction input files and not to impact file
   * descriptors for the same file used by user queries.
   * Suggest to enable {@link BlockBasedTableConfig#cacheIndexAndFilterBlocks()}
   * for this mode if using block-based table.
   *
   * Default: false
   *
   * @return true if a new file descriptor and table reader are created for
   *     compaction inputs
   */
  boolean newTableReaderForCompactionInputs();

  /**
   * If non-zero, we perform bigger reads when doing compaction. If you're
   * running RocksDB on spinning disks, you should set this to at least 2MB.
   *
   * That way RocksDB's compaction is doing sequential instead of random reads.
   * When non-zero, we also force {@link #newTableReaderForCompactionInputs()}
   * to true.
   *
   * Default: 0
   *
   * @param compactionReadaheadSize The compaction read-ahead size
   *
   * @return the reference to the current options.
   */
  T setCompactionReadaheadSize(final long compactionReadaheadSize);

  /**
   * If non-zero, we perform bigger reads when doing compaction. If you're
   * running RocksDB on spinning disks, you should set this to at least 2MB.
   *
   * That way RocksDB's compaction is doing sequential instead of random reads.
   * When non-zero, we also force {@link #newTableReaderForCompactionInputs()}
   * to true.
   *
   * Default: 0
   *
   * @return The compaction read-ahead size
   */
  long compactionReadaheadSize();

  /**
   * This is a maximum buffer size that is used by WinMmapReadableFile in
   * unbuffered disk I/O mode. We need to maintain an aligned buffer for
   * reads. We allow the buffer to grow until the specified value and then
   * for bigger requests allocate one shot buffers. In unbuffered mode we
   * always bypass read-ahead buffer at ReadaheadRandomAccessFile
   * When read-ahead is required we then make use of
   * {@link #compactionReadaheadSize()} value and always try to read ahead.
   * With read-ahead we always pre-allocate buffer to the size instead of
   * growing it up to a limit.
   *
   * This option is currently honored only on Windows
   *
   * Default: 1 Mb
   *
   * Special value: 0 - means do not maintain per instance buffer. Allocate
   *                per request buffer and avoid locking.
   *
   * @param randomAccessMaxBufferSize the maximum size of the random access
   *     buffer
   *
   * @return the reference to the current options.
   */
  T setRandomAccessMaxBufferSize(long randomAccessMaxBufferSize);

  /**
   * This is a maximum buffer size that is used by WinMmapReadableFile in
   * unbuffered disk I/O mode. We need to maintain an aligned buffer for
   * reads. We allow the buffer to grow until the specified value and then
   * for bigger requests allocate one shot buffers. In unbuffered mode we
   * always bypass read-ahead buffer at ReadaheadRandomAccessFile
   * When read-ahead is required we then make use of
   * {@link #compactionReadaheadSize()} value and always try to read ahead.
   * With read-ahead we always pre-allocate buffer to the size instead of
   * growing it up to a limit.
   *
   * This option is currently honored only on Windows
   *
   * Default: 1 Mb
   *
   * Special value: 0 - means do not maintain per instance buffer. Allocate
   *                per request buffer and avoid locking.
   *
   * @return the maximum size of the random access buffer
   */
  long randomAccessMaxBufferSize();

  /**
   * This is the maximum buffer size that is used by WritableFileWriter.
   * On Windows, we need to maintain an aligned buffer for writes.
   * We allow the buffer to grow until it's size hits the limit.
   *
   * Default: 1024 * 1024 (1 MB)
   *
   * @param writableFileMaxBufferSize the maximum buffer size
   *
   * @return the reference to the current options.
   */
  T setWritableFileMaxBufferSize(long writableFileMaxBufferSize);

  /**
   * This is the maximum buffer size that is used by WritableFileWriter.
   * On Windows, we need to maintain an aligned buffer for writes.
   * We allow the buffer to grow until it's size hits the limit.
   *
   * Default: 1024 * 1024 (1 MB)
   *
   * @return the maximum buffer size
   */
  long writableFileMaxBufferSize();

  /**
   * Use adaptive mutex, which spins in the user space before resorting
   * to kernel. This could reduce context switch when the mutex is not
   * heavily contended. However, if the mutex is hot, we could end up
   * wasting spin time.
   * Default: false
   *
   * @param useAdaptiveMutex true if adaptive mutex is used.
   * @return the instance of the current object.
   */
  T setUseAdaptiveMutex(boolean useAdaptiveMutex);

  /**
   * Use adaptive mutex, which spins in the user space before resorting
   * to kernel. This could reduce context switch when the mutex is not
   * heavily contended. However, if the mutex is hot, we could end up
   * wasting spin time.
   * Default: false
   *
   * @return true if adaptive mutex is used.
   */
  boolean useAdaptiveMutex();

  /**
   * Allows OS to incrementally sync files to disk while they are being
   * written, asynchronously, in the background.
   * Issue one request for every bytes_per_sync written. 0 turns it off.
   * Default: 0
   *
   * @param bytesPerSync size in bytes
   * @return the instance of the current object.
   */
  T setBytesPerSync(long bytesPerSync);

  /**
   * Allows OS to incrementally sync files to disk while they are being
   * written, asynchronously, in the background.
   * Issue one request for every bytes_per_sync written. 0 turns it off.
   * Default: 0
   *
   * @return size in bytes
   */
  long bytesPerSync();

  /**
   * Same as {@link #setBytesPerSync(long)} , but applies to WAL files
   *
   * Default: 0, turned off
   *
   * @param walBytesPerSync size in bytes
   * @return the instance of the current object.
   */
  T setWalBytesPerSync(long walBytesPerSync);

  /**
   * Same as {@link #bytesPerSync()} , but applies to WAL files
   *
   * Default: 0, turned off
   *
   * @return size in bytes
   */
  long walBytesPerSync();

  /**
   * If true, then the status of the threads involved in this DB will
   * be tracked and available via GetThreadList() API.
   *
   * Default: false
   *
   * @param enableThreadTracking true to enable tracking
   *
   * @return the reference to the current options.
   */
  T setEnableThreadTracking(boolean enableThreadTracking);

  /**
   * If true, then the status of the threads involved in this DB will
   * be tracked and available via GetThreadList() API.
   *
   * Default: false
   *
   * @return true if tracking is enabled
   */
  boolean enableThreadTracking();

  /**
   * The limited write rate to DB if
   * {@link ColumnFamilyOptions#softPendingCompactionBytesLimit()} or
   * {@link ColumnFamilyOptions#level0SlowdownWritesTrigger()} is triggered,
   * or we are writing to the last mem table allowed and we allow more than 3
   * mem tables. It is calculated using size of user write requests before
   * compression. RocksDB may decide to slow down more if the compaction still
   * gets behind further.
   *
   * Unit: bytes per second.
   *
   * Default: 16MB/s
   *
   * @param delayedWriteRate the rate in bytes per second
   *
   * @return the reference to the current options.
   */
  T setDelayedWriteRate(long delayedWriteRate);

  /**
   * The limited write rate to DB if
   * {@link ColumnFamilyOptions#softPendingCompactionBytesLimit()} or
   * {@link ColumnFamilyOptions#level0SlowdownWritesTrigger()} is triggered,
   * or we are writing to the last mem table allowed and we allow more than 3
   * mem tables. It is calculated using size of user write requests before
   * compression. RocksDB may decide to slow down more if the compaction still
   * gets behind further.
   *
   * Unit: bytes per second.
   *
   * Default: 16MB/s
   *
   * @return the rate in bytes per second
   */
  long delayedWriteRate();

  /**
   * If true, allow multi-writers to update mem tables in parallel.
   * Only some memtable factorys support concurrent writes; currently it
   * is implemented only for SkipListFactory.  Concurrent memtable writes
   * are not compatible with inplace_update_support or filter_deletes.
   * It is strongly recommended to set
   * {@link #setEnableWriteThreadAdaptiveYield(boolean)} if you are going to use
   * this feature.
   * Default: false
   *
   * @param allowConcurrentMemtableWrite true to enable concurrent writes
   *     for the memtable
   *
   * @return the reference to the current options.
   */
  T setAllowConcurrentMemtableWrite(boolean allowConcurrentMemtableWrite);

  /**
   * If true, allow multi-writers to update mem tables in parallel.
   * Only some memtable factorys support concurrent writes; currently it
   * is implemented only for SkipListFactory.  Concurrent memtable writes
   * are not compatible with inplace_update_support or filter_deletes.
   * It is strongly recommended to set
   * {@link #setEnableWriteThreadAdaptiveYield(boolean)} if you are going to use
   * this feature.
   * Default: false
   *
   * @return true if concurrent writes are enabled for the memtable
   */
  boolean allowConcurrentMemtableWrite();

  /**
   * If true, threads synchronizing with the write batch group leader will
   * wait for up to {@link #writeThreadMaxYieldUsec()} before blocking on a
   * mutex. This can substantially improve throughput for concurrent workloads,
   * regardless of whether {@link #allowConcurrentMemtableWrite()} is enabled.
   * Default: false
   *
   * @param enableWriteThreadAdaptiveYield true to enable adaptive yield for the
   *     write threads
   *
   * @return the reference to the current options.
   */
  T setEnableWriteThreadAdaptiveYield(
      boolean enableWriteThreadAdaptiveYield);

  /**
   * If true, threads synchronizing with the write batch group leader will
   * wait for up to {@link #writeThreadMaxYieldUsec()} before blocking on a
   * mutex. This can substantially improve throughput for concurrent workloads,
   * regardless of whether {@link #allowConcurrentMemtableWrite()} is enabled.
   * Default: false
   *
   * @return true if adaptive yield is enabled
   *    for the writing threads
   */
  boolean enableWriteThreadAdaptiveYield();

  /**
   * The maximum number of microseconds that a write operation will use
   * a yielding spin loop to coordinate with other write threads before
   * blocking on a mutex.  (Assuming {@link #writeThreadSlowYieldUsec()} is
   * set properly) increasing this value is likely to increase RocksDB
   * throughput at the expense of increased CPU usage.
   * Default: 100
   *
   * @param writeThreadMaxYieldUsec maximum number of microseconds
   *
   * @return the reference to the current options.
   */
  T setWriteThreadMaxYieldUsec(long writeThreadMaxYieldUsec);

  /**
   * The maximum number of microseconds that a write operation will use
   * a yielding spin loop to coordinate with other write threads before
   * blocking on a mutex.  (Assuming {@link #writeThreadSlowYieldUsec()} is
   * set properly) increasing this value is likely to increase RocksDB
   * throughput at the expense of increased CPU usage.
   * Default: 100
   *
   * @return the maximum number of microseconds
   */
  long writeThreadMaxYieldUsec();

  /**
   * The latency in microseconds after which a std::this_thread::yield
   * call (sched_yield on Linux) is considered to be a signal that
   * other processes or threads would like to use the current core.
   * Increasing this makes writer threads more likely to take CPU
   * by spinning, which will show up as an increase in the number of
   * involuntary context switches.
   * Default: 3
   *
   * @param writeThreadSlowYieldUsec the latency in microseconds
   *
   * @return the reference to the current options.
   */
  T setWriteThreadSlowYieldUsec(long writeThreadSlowYieldUsec);

  /**
   * The latency in microseconds after which a std::this_thread::yield
   * call (sched_yield on Linux) is considered to be a signal that
   * other processes or threads would like to use the current core.
   * Increasing this makes writer threads more likely to take CPU
   * by spinning, which will show up as an increase in the number of
   * involuntary context switches.
   * Default: 3
   *
   * @return writeThreadSlowYieldUsec the latency in microseconds
   */
  long writeThreadSlowYieldUsec();

  /**
   * If true, then DB::Open() will not update the statistics used to optimize
   * compaction decision by loading table properties from many files.
   * Turning off this feature will improve DBOpen time especially in
   * disk environment.
   *
   * Default: false
   *
   * @param skipStatsUpdateOnDbOpen true if updating stats will be skipped
   *
   * @return the reference to the current options.
   */
  T setSkipStatsUpdateOnDbOpen(boolean skipStatsUpdateOnDbOpen);

  /**
   * If true, then DB::Open() will not update the statistics used to optimize
   * compaction decision by loading table properties from many files.
   * Turning off this feature will improve DBOpen time especially in
   * disk environment.
   *
   * Default: false
   *
   * @return true if updating stats will be skipped
   */
  boolean skipStatsUpdateOnDbOpen();

  /**
   * Recovery mode to control the consistency while replaying WAL
   *
   * Default: {@link WALRecoveryMode#PointInTimeRecovery}
   *
   * @param walRecoveryMode The WAL recover mode
   *
   * @return the reference to the current options.
   */
  T setWalRecoveryMode(WALRecoveryMode walRecoveryMode);

  /**
   * Recovery mode to control the consistency while replaying WAL
   *
   * Default: {@link WALRecoveryMode#PointInTimeRecovery}
   *
   * @return The WAL recover mode
   */
  WALRecoveryMode walRecoveryMode();

  /**
   * if set to false then recovery will fail when a prepared
   * transaction is encountered in the WAL
   *
   * Default: false
   *
   * @param allow2pc true if two-phase-commit is enabled
   *
   * @return the reference to the current options.
   */
  T setAllow2pc(boolean allow2pc);

  /**
   * if set to false then recovery will fail when a prepared
   * transaction is encountered in the WAL
   *
   * Default: false
   *
   * @return true if two-phase-commit is enabled
   */
  boolean allow2pc();

  /**
   * A global cache for table-level rows.
   *
   * Default: null (disabled)
   *
   * @param rowCache The global row cache
   *
   * @return the reference to the current options.
   */
  T setRowCache(final Cache rowCache);

  /**
   * A global cache for table-level rows.
   *
   * Default: null (disabled)
   *
   * @return The global row cache
   */
  Cache rowCache();

  /**
   * If true, then DB::Open / CreateColumnFamily / DropColumnFamily
   * / SetOptions will fail if options file is not detected or properly
   * persisted.
   *
   * DEFAULT: false
   *
   * @param failIfOptionsFileError true if we should fail if there is an error
   *     in the options file
   *
   * @return the reference to the current options.
   */
  T setFailIfOptionsFileError(boolean failIfOptionsFileError);

  /**
   * If true, then DB::Open / CreateColumnFamily / DropColumnFamily
   * / SetOptions will fail if options file is not detected or properly
   * persisted.
   *
   * DEFAULT: false
   *
   * @return true if we should fail if there is an error in the options file
   */
  boolean failIfOptionsFileError();

  /**
   * If true, then print malloc stats together with rocksdb.stats
   * when printing to LOG.
   *
   * DEFAULT: false
   *
   * @param dumpMallocStats true if malloc stats should be printed to LOG
   *
   * @return the reference to the current options.
   */
  T setDumpMallocStats(boolean dumpMallocStats);

  /**
   * If true, then print malloc stats together with rocksdb.stats
   * when printing to LOG.
   *
   * DEFAULT: false
   *
   * @return true if malloc stats should be printed to LOG
   */
  boolean dumpMallocStats();

  /**
   * By default RocksDB replay WAL logs and flush them on DB open, which may
   * create very small SST files. If this option is enabled, RocksDB will try
   * to avoid (but not guarantee not to) flush during recovery. Also, existing
   * WAL logs will be kept, so that if crash happened before flush, we still
   * have logs to recover from.
   *
   * DEFAULT: false
   *
   * @param avoidFlushDuringRecovery true to try to avoid (but not guarantee
   *     not to) flush during recovery
   *
   * @return the reference to the current options.
   */
  T setAvoidFlushDuringRecovery(boolean avoidFlushDuringRecovery);

  /**
   * By default RocksDB replay WAL logs and flush them on DB open, which may
   * create very small SST files. If this option is enabled, RocksDB will try
   * to avoid (but not guarantee not to) flush during recovery. Also, existing
   * WAL logs will be kept, so that if crash happened before flush, we still
   * have logs to recover from.
   *
   * DEFAULT: false
   *
   * @return true to try to avoid (but not guarantee not to) flush during
   *     recovery
   */
  boolean avoidFlushDuringRecovery();

  /**
   * By default RocksDB will flush all memtables on DB close if there are
   * unpersisted data (i.e. with WAL disabled) The flush can be skip to speedup
   * DB close. Unpersisted data WILL BE LOST.
   *
   * DEFAULT: false
   *
   * Dynamically changeable through
   *     {@link RocksDB#setOptions(ColumnFamilyHandle, MutableColumnFamilyOptions)}
   *     API.
   *
   * @param avoidFlushDuringShutdown true if we should avoid flush during
   *     shutdown
   *
   * @return the reference to the current options.
   */
  T setAvoidFlushDuringShutdown(boolean avoidFlushDuringShutdown);

  /**
   * By default RocksDB will flush all memtables on DB close if there are
   * unpersisted data (i.e. with WAL disabled) The flush can be skip to speedup
   * DB close. Unpersisted data WILL BE LOST.
   *
   * DEFAULT: false
   *
   * Dynamically changeable through
   *     {@link RocksDB#setOptions(ColumnFamilyHandle, MutableColumnFamilyOptions)}
   *     API.
   *
   * @return true if we should avoid flush during shutdown
   */
  boolean avoidFlushDuringShutdown();
}
